The present invention relates to a useful serine/threonine protein kinase, a DNA encoding the protein kinase, a vector comprising the DNA, a host harboring the vector, and an antibody that binds to the protein kinase.
Protein kinase is an enzyme that phosphorylates serine, threonine, or tyrosine residues of substrate proteins, and numerous protein kinase families are known. It is known that protein kinase controls various biological phenomena by regulating the intracellular signal transduction system through protein phosphorylation (Hunter, T., A thousand and one protein kinases, Cell, 50:823-829, 1987).
One of a group of nematode (C. elegans) mutants (uncoordinated), xe2x80x9cunc-51,xe2x80x9d causes movement disorder and a responsible gene xe2x80x9cUNC-51 xe2x80x9d found in unc-51 reportedly encodes a novel serine/threonine protein kinase (Ogura, K. et al., Caenorhabditis elegans unc-51 gene required for axonal elongation encodes a novel serine/threonine kinase, Genes Dev., 8:2389-2400, 1994). The result of tissue staining confirmed that the unc-51 mutant has axonal elongation disorder, and the UNC-51 kinase gene was thought to be essential for axonal elongation (Ogura, K. et al., Caenorhabditis elegans unc-51 gene required for axonal elongation encodes a novel serine/threonine kinase, Genes Dev., 8:2389-2400, 1994).
The mechanism of axonal biosynthesis in mammals has not been revealed yet at the molecular level. C. elegans is an excellent experimental model for axonal biosynthesis, and the involvement of similar molecules in both mammals and C. elegans has been suggested. The isolation of mammalian molecule having the similar function as the UNC-51 kinase of the nematode has been desired.
An objective of the present invention is to provide a mammalian serine/threonine protein kinase involved in axonal formation.
As a result of research to achieve the above objective, the inventors successfully isolated a mouse cDNA encoding a protein comprising a serine/threonine protein kinase region by effecting PCR using a synthetic DNA corresponding to the kinase-conserved region as a primer and a rat cDNA as a template, and screening a mouse cDNA library using the DNA fragment thus obtained as a probe. The multiple human and mouse cDNAs having the similar structure to the isolated mouse cDNA were successfully isolated based on the sequence of the isolated mouse cDNA. The inventors synthesized an antisense DNA against the isolated mouse cDNA, and its effect on a nerve cell was studied to confirm that the antisense DNA inhibits axonal elongation.
The present invention relates to a mammalian serine/threonine protein kinase involved in axonal formation. More specifically, the invention relates to:
(1) a protein comprising the amino acid sequence set forth in SEQ ID NO: 2, 4, 14, 16, or 21, or a protein comprising the amino acid sequence set forth in SEQ ID NO: 2, 4, 14, 16, or 21, in which one or more amino acids are substituted, deleted, or added, wherein said protein has activity of serine/threonine protein kinase;
(2) a protein encoded by a DNA hybridizing with a DNA comprising the nucleotide sequence set forth in SEQ ID NO: 1, 3, 13, 15, or 20, wherein said protein has the activity of serine/threonine protein kinase;
(3) a protein comprising the amino acid sequence set forth in SEQ ID NO: 2, 4, 14, 16, or 21, or a protein comprising the amino acid sequence set forth in SEQ ID NO: 2, 4, 14, 16, or 21, in which one or more amino acids are substituted, deleted, or added, wherein said protein induces axonal elongation;
(4) a protein encoded by a DNA hybridizing with a DNA comprising the nucleotide sequence set forth in SEQ ID NO: 1, 3, 13, 15, or 20, wherein said protein induces axonal elongation;
(5) the protein of (2) or (4), wherein said protein is derived from a mammal;
(6) a DNA encoding any one of the proteins of (1) to (5);
(7) an antisense DNA against a DNA comprising the nucleotide sequence set forth in SEQ ID NO: 1, 3, 13, 15, or 20 or a part thereof, wherein said DNA or a part thereof-inhibits axonal elongation;
(8) a vector comprising the DNA of (6) or (7);
(9) a host cell harboring the vector of (8); and
(10) an antibody that binds to the protein of (1) or (2).
A xe2x80x9cproteinxe2x80x9d used herein includes a peptide with a short amino acid sequence.
The present invention relates to a mammal-derived serine/threonine protein kinase involved in axonal formation. The inventors isolated a mouse cDNA highly homologous to the kinase region of UNC-51, a serine/threonine kinase that induces axonal elongation in a nematode, C. elegans (Ogura, K. et al., Caenorhabditis elegans unc-51 gene required for axonal elongation encodes a novel serine/threonine kinase, Genes Dev., 8:2389-2400, 1994) (this clone was named xe2x80x9cMUK1xe2x80x9d). The nucleotide sequence of the MUK1 cDNA is shown in SEQ ID NO: 1. The inventors also isolated four cDNAs comprising the similar structure to the MUK1 cDNA by screening a human cerebellum library, a mouse cerebellum library, a human NH-2 cell library, and a mouse brain library, based on the sequence of MUK1. The isolated four cDNAs were considered to be a human counterpart (SEQ ID NO: 3), a splicing valiant (SEQ ID NO: 13), a human homologue (SEQ ID NO: 15), and a family gene (SEQ ID NO: 20) (named xe2x80x9cMUK2xe2x80x9d) of MUK1 considering their structural characteristics. The analysis of structures of the proteins encoded by these isolated cDNAs confirmed that all the proteins possess the kinase-conserved region. This fact indicates that those proteins would be involved in signal transduction through phosphorylation of other proteins. When an antisense DNA against the MUK1 cDNA (SEQ ID NO: 8) was added to Neuro2A cells derived from neuroblast cells, axonal elongation in the cells was inhibited. Those proteins may thus be involved in axonal elongation by signal transduction through phosphorylation of other proteins.
Among these proteins, the protein (SEQ ID NO: 4) encoded by cDNA set forth in SEQ ID NO: 3 is a partial sequence comprising the sequence corresponding to the serine/threonine protein kinase region. A protein encoded by the full-length DNA can be obtained by methods well known in the art. For example, the full-length DNA is isolated by screening a library with a partial sequence of the DNA of SEQ ID NO: 3 as probe or by PCR (Current protocols in Molecular Biology ed. by Ausubel et al. (1987) published by John Wiley and Sons, Section 6.1-6.4), the isolated full-length DNA is introduced into cultured cells such as COS cells to express the protein in the cells (Current Protocols in Molecular Biology, ed. by Ausubel et al. (1987) published by John Wiley and Sons, Section 9.1-9.9), then the protein is purified. The thus-isolated protein is also included in the protein of this invention.
Functional equivalents to the protein set forth in SEQ ID NO: 2, 4, 14, 16, or 21 can be obtained by substituting amino acid residue(s) of these proteins using usually used methods such as site-directed mutagenesis (Current Protocols in Molecular Biology, ed. by Ausubel et al. (1987) published by John Wiley and Sons, Section 8.1-8.5). This invention also includes proteins functionally equivalent to the protein of SEQ ID NO: 2, 4, 14, 16, or 21, in which one or more amino acids are substituted, deleted, or added. Alternatively, functionally equivalent proteins to the protein of SEQ ID NO: 2, 4, 14, 16, or 21 can be obtained by isolating DNAs highly homologous to DNA sequences (or a part thereof) of SEQ ID NO: 1, 3, 13, 15, and 20, using the known hybridization technique (Current Protocols in Molecular Biology, ed. by Ausubel et al. (1987) published by John Wiley and Sons, Sections 6.3, 6.4). The protein of the present invention includes such proteins functionally equivalent to the proteins of SEQ ID NO: 2, 4, 14, 16, and 21, encoded by a DNA hybridizing with the DNA of SEQ ID NO: 1, 3, 13, 15, or 20. The functionally equivalent proteins obtained by the hybridization technique are highly homologous in the amino acid sequence to the protein of SEQ ID NO: 2, 4, 14, 16, or 21 in general. High homology is preferably 60% or more, more preferably 80% or more, and most preferably 95% or more. The hybridization and washing conditions for isolating DNA encoding a functionally equivalent protein are defined as low stringency: 37xc2x0 C., 1xc3x97SSC, 0.1% SDS; moderate stringency: 42xc2x0 C., 0.5xc3x97SSC, 0.1% SDS; and high stringency: 65xc2x0 C., 0.2xc3x97SSC, 0.1% SDS. The xe2x80x9cDNA hybridizing withxe2x80x9d used herein include not only full-length DNAs hybridizing with the DNA of SEQ ID NO: 1, 3, 13, 15, or 20, but also DNAs comprising a region hybridizing with the above DNA. A xe2x80x9cfunctionally equivalent proteinxe2x80x9d means a protein that having the serine/threonine protein kinase activity similar to that of the protein of SEQ ID NO: 2, 4, 14, 16, or 21, and/or induces axonal elongation. xe2x80x9cSerine/threonine protein kinase activityxe2x80x9d means biochemical activity to phosphorylate substrate proteins and cellular biological activity induced by this biochemical activity. The biochemical activity of the serine/threonine protein kinase can be detected as autophosphorylationxe2x80x94and phosphorylation of basic proteins (such as a myelin basic protein, histone, or tau protein) in the presence of magnesium ions and ATP (Protein Kinase and Phosphatase, D. G. Hardie, translated by H. Hidaka, Medical Science International, p101-120). On the other hand, the biological activity can be detected as the cellular change when a DNA encoding serine/threonine protein kinase or its variant is expressed in cells (Muramatsu, M. et al., Protein Kinase and Signal Transduction: Studies with mutant protein kinases (1993) p185-192, The mechanism and new approach on drug resistance of cancer cells, The Elsevier Science Publishers). The xe2x80x9caxonal elongation-inducing activityxe2x80x9d can be detected by, for example, by introducing a DNA encoding the protein of the invention into cultured nerve cells such as Nero2A cells, PC12 cells, and NT-2 cells (Stratagene) and observing the cells under a phase-contrast microscope (Ulloa, et al., Depletion of casein kinase II by antisense oligonucleotide prevents neuritogenesis in neuroblastoma cells, EMBO. J., 12:1633-1640, 1993).
The protein of the present invention can be prepared as a recombinant protein or a natural protein. A recombinant protein can be prepared, for example, by inserting a DNA encoding the protein of the invention (e.g., the DNA of SEQ ID NO: 1, 3, 13, 15, or 20) into an appropriate expression vector, introducing the vector into a host cell, expressing the protein in the transformant, and purifying the protein, as described later. A natural protein can be prepared by the standard methods, for example, using an affinity column with an antibody (Current Protocols in Molecular Biology ed. by Ausubel et al. (1987) published by John and Wiley and Sons, Section 16.1-16.19). The antibody can be either a monoclonal antibody or a polyclonal antibody. A polyclonal antibody can be obtained by synthesizing oligopeptides corresponding to the amino acid sequence of interest and immunizing a rabbit with it, following the standard method (Current Protocols in Molecular Biology ed. by Ausubel et al. (1987) published by John Wiley and Sons, Section 11.12-11.13). A monoclonal antibody can be prepared by immunizing a mouse with a purified protein of interest expressed in E. coli by a standard method, fusing a spleen cell and a myeloma cell to produce hybridoma cells, and then obtaining a monoclonal antibody from the hybridoma (Current Protocols in Molecular Biology ed. by Ausubel et al. (1987) published by John Wiley and Sons, Section 11.4-11.11). When an antibody that binds to the protein of the invention is used for antibody therapy, a human antibody or a humanized antibody that has low immunogenicity is preferably used. A human antibody can be prepared, for example, by immunizing a mouse whose immune system is replaced by the human system in the same manner as described above for producing the monoclonal antibody. A humanized antibody can be prepared by the recombinant DNA technology using hypervariable region of the monoclonal antibody (Methods in Enzymology, 203:99-121, 1991).
This invention also relates to the DNA encoding the above-described protein of the invention. The form of the DNA of the invention is not particularly limited as long as it encodes the protein of the invention, including cDNA, genomic DNA, chemically synthesized DNA, etc. The DNA of the present invention can be isolated by the standard method, such as the hybridization method using the DNA sequence of SEQ ID NO: 1, 3, 13, 15, or 20 as a probe, or PCR using the primers synthesized based on these DNA sequences. The DNA of the invention can be used to prepare recombinant proteins. That is, the protein of the invention can be prepared as a recombinant protein by inserting the DNA of this invention in an appropriate vector, introducing the vector into a host cell, and culturing the transformant. Any vector capable of stably maintaining the inserted DNA can be used without limitation. For example, Bluescript vector (Stratagene) is preferable when a host cell is E. coli. When a vector is used to produce the protein of the invention, an expression vector is especially useful. Any expression vector can be used without limitation as long as it expresses the protein of this invention in vitro, in E. coli, in a cultured cell line, or in vivo. For example, pBEST vector (Promega) is preferably used for expression in vitro, and pET vector (Invitrogen) for E. coli, pME18S vector (Mol Cell Biol. 8:466-472, 1988) for cultured cell lines and in vivo. The DNA of the invention can be inserted into a vector by the methods well known in the art, for example, ligation at the restriction enzyme site (Current Protocols in Molecular Biology ed. by Ausubel et al. (1987) published by John Wiley and Sons, Section 11. 4-11.11). A vector can be introduced into any host cell without limitation. For example, a cell capable of overexpressing the protein, such as COS cells and CHO cells, can be used. A vector can be introduced into a host cell by the method well known in the art, such as calcium phosphate precipitation, electroporation (Current Protocols in Molecular Biology ed. by Ausubel et al. (1987) published by John Wiley and Sons, Section 9.1-9.9), the lipofectamine method (GIBCO-BRL), or microinjection.
The DNA and its antisense DNA of the present invention can be used for promoting or inhibiting axonal elongation. Therefore, those DNAs are useful for diagnosis and gene therapy of various inherited neuropathy, senile dementia, Alzheimer""s disease, and psychoneurosis, which cause axonal elongation disorder. For gene therapy, the above DNA or antisense DNA is inserted into a retrovirus vector or an adenovirus vector- and administered to a patient by the in vivo or ex vivo method. The antisense DNA can be prepared, for example, by the phosphorothioate method (Stein, 1988 Physicochemical properties of phosphorothioate oligodeoxynucleotides, Nucleic Acids Res. 16:3209-3221, 1988) based on the DNA sequence information of the invention (for example, the DNA of SEQ ID NO: 1, 3, 13, 15, or 20). The axonal elongation-inhibitory activity of the thus-prepared antisense DNA can be detected by observing cultured nerve cells such as Nero2A cells, PC12 cells, and NT-2 cells (Stratagene), into which the antisense DNA was introduced, under a phase-contrast microscope (Ulloa et al., Depletion of casein kinase II by antisense oligonucleotide prevents neuritogenesis in neuroblastoma cells, EMBO. J., 12:1633-1640, 1993).
An xe2x80x9cisolated nucleic acidxe2x80x9d is a nucleic acid the structure of which is not identical to that of any naturally occurring nucleic acid or to that of any fragment of a naturally occurring genomic nucleic acid spanning more than three separate genes. The term therefore covers, for example, (a) a DNA which has the sequence of part of a naturally occurring genomic DNA molecule but is not flanked by both of the coding sequences that flank that part of the molecule in the genome of the organism in which it naturally occurs; (b) a nucleic acid incorporated into a vector or into the genomic DNA of a prokaryote or eukaryote in a manner such that the resulting molecule is not identical to any naturally occurring vector or genomic DNA; (c) a separate molecule such as a cDNA, a genomic fragment, a fragment produced by polymerase chain reaction (PCR), or a restriction fragment; and (d) a recombinant nucleotide sequence that is part of a hybrid gene, i.e., a gene encoding a fusion protein. Specifically excluded from this definition are nucleic acids present in mixtures of different (i) DNA molecules, (ii) transfected cells, or (iii) cell clones: e.g., as these occur in a DNA library such as a cDNA or genomic DNA library.
The term xe2x80x9csubstantially purexe2x80x9d as used herein in reference to a given polypeptide means that the polypeptide is substantially free from other biological compounds, such as those in cellular material, viral material, or culture medium, with which the polypeptide was associated (e.g., in the course of production by recombinant DNA techniques or before purification from a natural biological source). The substantially pure polypeptide is at least 75% (e.g., at least 80, 85, 95, or 99%) pure by dry weight. Purity can be measured by any appropriate standard method, for example, by column chromatography, polyacrylamide gel electrophoresis, or HPLC analysis.
A xe2x80x9cconservative amino acid substitutionxe2x80x9d is one in which an amino acid residue is replaced with another residue having a chemically similar side chain. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine).
As used herein, xe2x80x9cpercent identityxe2x80x9d of two amino acid sequences or of two nucleic acids is determined using the algorithm of Karlin and Altschul (Proc. Natl. Acad. Sci. USA 87:2264-2268, 1990), modified as in Karlin and Altschul (Proc. Natl. Acad. Sci. USA 90:5873-5877, 1993). Such an algorithm is incorporated into the NBLAST and XBLAST programs of Altschul et al. (J. Mol. Biol. 215:403-410, 1990). BLAST nucleotide searches are performed with the NBLAST program, score=100, wordlength=12 to obtain nucleotide sequences homologous to a nucleic acid molecules of the invention. BLAST protein searches are performed with the XBLAST program, score=50, wordlength=3 to obtain amino acid sequences homologous to a reference polypeptide. To obtain gapped alignments for comparison purposes, Gapped BLAST is utilized as described in Altschul et al. (Nucleic Acids Res. 25:3389-3402, 1997). When utilizing BLAST and Gapped BLAST programs, the default parameters of the respective programs (e.g., XBLAST and NBLAST) are used. See http://www.ncbi.nlm.nih.gov.
By xe2x80x9cinhibitingxe2x80x9d is meant any measurable level of inhibition, including, for example, 100% or 10% inhibition.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present application, including definitions, will control. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference. The materials, methods, and examples are illustrative only and not intended to be limiting. Other features and advantages of the invention will be apparent from the detailed description, and from the claims.